At Holloman, magnetic levitation is on the fast-track

HOLLOMAN AIR FORCE BASE The 846th Test Squadron successfully performed its most ambitious test to date on the magnetic levitation track at Holloman Air Force Base on Feb. 7. Members of the 846th were able to use the Maglev track in conjunction with a new propulsion system to reach an astounding speed of more than 500 mph.

"We went faster than we've ever gone before," said Jim Daniel, 846th Test Squadron business development manager, "and that causes all kinds of interesting risks. In this business, there's a lot of risk in the unknown, and we've never tested the Maglev system under these conditions."

As Daniel explains, what makes the Maglev track so extraordinary, is its ability to mimic flight conditions by drastically reducing the amount of vibration felt by the object being tested. The track enables this effect through the use of four superconductive electromagnets that attach to the test sled like wheels on a car. Once charged with a current, the magnets are able to generate enough force to lift the sled about one inch off the track throughout the duration of the rocket propulsion.

Part of what makes the magnets so unique is their ability to display a phenomenon known as superconductivity. Once the magnets are in this state, they have exactly zero electrical resistance, meaning they can maintain a charge without an active current flowing into them. However, in order to reach this state, the magnets must be cooled below their characteristic critical temperature, approximately minus 450 degrees Fahrenheit.

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In order to get the magnets to be this cold, liquid helium must be pumped into the magnets until they are cold enough to hold a current. This passive system of charging the magnets differs from the active kind of magnetic levitation used in bullet trains that requires a constant source of electricity. As long as the magnets are cold enough and charged, no additional electrical power is required for them to be able to lift the sled.

Much of the technology used to complete the test was provided to the 846th by General Atomics, the primary contractor of the Maglev track.

"What we were trying to do was prove the system," said Daniel, "make sure that it works at higher speeds, and as a subtext of what was going on, we were trying to transition from General Atomics operating the system, to the Air Force operating the system. So it was a test for data and a test to confirm our initial operating capability. Through the completion of this test, we are truly able to claim the Maglev system as an Air Force asset."

Though the Maglev track has been tested before, this most recent test pushed its capabilities to the max.

As Daniel describes, six improved Zuni rockets were attached to the sled to provide the thrust necessary to reach the new speed. The sled was aligned along sophisticated dual-track beams made of concrete and embedded with copper, which repelled the magnets to allow for more stabilization.

"There are lots of forces at play with the testing of the Maglev system, you have magnetic forces, the forces from the rocket motors and the forces from the air drag. All of these forces are fluctuating as the test is being performed and part of our goal was to determine exactly how they interact with one another so that we can learn more about our capability with magnetic levitation."

The Maglev's success at Holloman allows the 846th to provide a ground-based test environment that can accurately simulate the vibrations of a real flight test. Daniel explains that the smoothness of the ride is the Maglev's key asset. With the stability that the Maglev track can offer, the most delicate components of a payload can be preserved intact throughout the duration of a test.

"It's a more benign environment," said Lt. Col. Keith Roessig, 846th Test Squadron commander, "the magnetic forces lifting and keeping the sled in the guide way reproduce very closely the aerodynamic loads seen during flight. With temperature, load and vibration instrumentation on the sled combined with high-speed camera footage of the test as it takes place, a complete record of the event is captured for further analysis. As an alternative to flight tests, the Maglev and the traditional steel rail can acquire roughly 90 percent of the data needed at about 10 percent of the cost."

The test that took place Feb. 7 was the culmination of nearly two decades of intensive research and engineering. On the day of the test, several General Atomics personnel came to witness as the Air Force used the technology they developed to break new ground in magnetic levitation.

"The most exciting part of this test, beyond just the sheer display of power from the rockets, is being able to tell people that we now have this unique capability available using only Air Force personnel and assets," Roessig said. "We're now able to provide quality test data to program offices for a whole new set of electronic systems at a fraction of the risk and cost inherent in flight test. This could truly be the next generation of test track."